Page 217 - WCS - Electrical

WORKSHOP CALCULATION & SCIENCE - CITS

2 Vacuum pressure Atmospheric pressure

P abs = P atm - P Vaccum

Pressure Measuring Instrument

Manometers Mechanical Gauge
1 Diaphragm pressure gauge
2 Bourdon Tube pressure
Simple Micromanometer Differential gauge
Manometer Manometer 3 Dead weight pressure gauge
1 Piezometer 1 U - tube differential 4 Bellow pressure gauge
2 U - tube Manometer Manometer
3 Single Column manometer 2 Inverted U - tube
a Vertical column manometer differential Manometer
b Inclined column manometer

Manometer
It is the device used for measuring the pressure at a point in a fluid by balancing the column of fluid by another
column of fluid.

It is used to measure the pressure in pipes and channels.
Simple Manometers
A simple manometer consists of a glass tube having one of its ends connected to a point where pressure is to be
measured and other end remains open to atmosphere. Common types of simple manometers are:
1 Piezometer
2 U-tube Manometers
3 Single Column Manometers
1 Piezometer
It is the simplest form of manometer used for measuring gauge pressures.
One end of this manometer is connected to the point where pressure is to be measured and other end is open to
the atmosphere as shown in Fig.
The rise of liquid gives the pressure head at that point. If at a point A, the height of liquid is h in piezometer tube,
then pressure at A
Mechanical Pressure Gauges
It is the device used for measuring the pressure at a point in a fluid at very high pressure
It gives direct pressure reading
They are portable
Bourdon Tube Gauge
• The most commonly used mechanical gauge is Bourdon type pressure gauge.
• It is a stiff, flattened metal tube bent into a circular shape.
• The fluid whose pressure is to be measured is inside the tube.
• One end of the tube is fixed and other end is free to move inward or outward.
• The inward and outward movement of free end moves a pointer, through a linkage and gear arrangement, a
dial graduated in pressure unit i.e. bar.
• The movement of the free end of the Bourdon tube is proportional to the difference between the external
atmospheric pressure and internal fluid pressure.

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CITS : WCS - Electrical - Exercise 19